1. Field of the Invention
This invention relates to a fuel injection valve for air-compressing internal combustion engines with fuel injection, particularly with direct fuel injection, comprising a nozzle holder, a nozzle body and a pintle, which is operable by the application of fuel pressure against the force of a closing spring, which is accommodated in a spring chamber of the nozzle holder and which pintle cooperates with a damper, which comprises a fuel-filled damper chamber, which opens into a constricted passage, and a separate damper piston, which is interposed between the pintle and the damper chamber and enters the damper chamber and is non-positively connected to the pintle.
2. Description of the Prior Art
In order to prevent a deformation of the pintle end of the pintle stop and to permit a control of the timing of the fuel injection proper, which timing will influence the combustion process and the quality of the combustion, it is known to provide a fuel injection valve with a damper, which comprises a separate damper piston for damping the movement of the pintle in the opening sense because that movement involves a displacement of the fluid out of the damper chamber through the constricted passage.
Whereas such a fuel injection valve has already been disclosed in GB-A-664 884, that known fuel injection valve can be combined only with a special constricted nozzle and does not permit the use of conventional nozzles, which are provided with a desired damper, and also does not permit the economical use of conventional components to a large extent.
DE-A-30 41 018 discloses a fuel injection valve in which the nozzle body has a bore which guides the pintle and has an end portion which is adjacent to the spring chamber of the nozzle holder and serves as a damper chamber. The pintle constitutes a displacer for displacing fuel contained in the damper chamber into the spring chamber through the constricted passage, which is formed in a disk or in an adapter disposed between the nozzle body and the nozzle holder. As a result an expensive alteration of the conventional fuel injection nozzles and the components thereof is required and the damping action is limited, particularly owing to the predetermined dimensions of the pintle, the thrust pin provided between the pintle and the mushroom-shaped abutment for the closing spring, and the damper chamber. Stronger damping actions cannot be achieved unless the constricted passage is extremely small, so that the manufacture will be virtually uncontrollable because the leakage losses may be of the same order as the rate of fuel being throttled. Besides, a separation of the pintle and the plunger would be desired but in that case these two components may be lifted from each other so that the damping action will be eliminated. Besides, the damper chamber adjoins the joint between the nozzle body and the adapter so that the high pressure in the damper chamber may give rise to problems due to leakage. For this reason that known damper may be used, at best, in fuel injection valves for engines having a precombustion chamber rather than in fuel injection valves for engines for direct fuel injection which are operated under much higher fuel injection pressures and with a smaller needle stroke and often with lower rated speeds so that much stronger damping actions are required.